Yolsal-Çevikbilen, Seda

Eken, Tuna

Abstract [en]

The November 12, 2017 Mw 7.4 earthquake that trembled near the border region between Halabjah (Iraq) andSarpol-e Zahab (Iran) is the largest ever-recorded earthquake in the Zagros Mountains since 1900. The epicenterlocation of the event suggests that the NNW trending Mountain Front Fault (MFF) has been responsible for theearthquake though it was not associated with surface faulting. Analysis of teleseismic P- and SH- body-waveformsdata indicate a well-constrained rupture propagated along the dip direction of the fault plane with an effectiverupture area of 80km long, 70km wide and focal depth of 192 km ENE dipping low-angle thrust faulting with asmall strike-slip component that produced little uplift in the region (Strike: 358o; Dip: 16o, Rake: 149o and SeismicMoment (Mo): 1.828x1020 N.m. with maximum displacement (Dmax) of 6.9m at hypocenter, and rupture velocity(Vr) of 3.2 km/s). The source rupture duration is about 45s, but the main moment release is observed in the first10s. Focal mechanism solution of the event indicates a NNW trending plane dipping 16 degrees ENE. This isin agreement with the dip direction of the MFF and the distribution of aftershocks covering an area some 50-70km wide. We explore its details in astonishment, if it is proved, that the Zagros Mountain Front fault (MFF) wasresponsible then it might have become curved at depth (?)To measure the co-seismic crustal deformation around the epicenter, we processed the ascending and descendingSentinel-1 SAR images, collected before and after the earthquake, by SNAP software and generated the interferogramsof surface deformation. The Differential InSAR (DInSAR) results show an upward and downward displacementsof 90 cm and 30 cm around the epicenter respectively. Furthermore, we investigate the differencebetween strike derived from seismological and that inferred from DInSAR satellite observations, and its possiblecauses.We do not have “best” or “right” rupture model yet, but just models satisfying for specific data sets. The aftermathof earthquakes like the 2017 Halabjah (Irak)-Sarpol-e Zahab (˙Iran) provides excellent opportunity to evaluate ourunderstanding of earthquakes and their hazards in the earthquake prone regions.

Aghamohamadi, Azadeh

Abstract [en]

In this study we present an up-to-date velocity field of Iran, including the largest number of data ever presentedon this region. It includes both a synthesis of all previously published campaign data (Raeesi et al., 2016) andall data from the Iranian Permanent GNSS Network (IPGN). The IPGN data cover some parts of Iran whichwere previously scarcely documented. These stations have been measured for 7 years. In total, more than 400instrumented sites are presented. From this velocity field, we calculated the strain rate.In this paper, we will show the contribution of this very dense velocity field to the detailed understanding of theactive tectonics of the various regions of Iran (Makran, Zagros, Alborz, ...).

Abstract [en]

This contribution reviews our current understanding of the tectonic development of the Amerasia Basin and presents new analogue modelling results relating to its formation. The Amerasia Basin is separated into the Canada Basin and the Makarov-Povodnikov basins by the Alpha-Mendeleev Ridges. Published data supports a conjugate relationship between the Alaskan and Canadian Arctic margins, in which counterclockwise rotation of Arctic Alaska from Arctic Canada resulted in the opening of the Canada Basin. Thus the tectonic development of the Canada Basin is ‘broadly’ understood, although its precise timing and the role of the Chukchi Plateau remain disputed. This leaves the Amerasia Basin and we identify two significant barriers to understanding its tectonic development: i) The northward extent of the Canada Basin fossil spreading ridge, and ii) the role of LIP magmatism. In assessing the former, we constructed a series of two-plate analogue models with properties homologous of homogeneous continental crust and simulated extension between the plates around a common rotation axis. In all models, a triangular (ocean) basin forms between the two ‘diverging’ plates, however, depending on the mode of opening and initial plate configuration transpressive, transtensive, and ‘pure’ strike-slip structures can be generated. Plates with a fixed pole of rotation that move at the same rate produce a basin that widens away from the pole along a straight ridge, whereas models with a migrating pole of rotation produce a bend in the spreading ridge and this may explain the curved ridge observed in the Canada Basin. Both models produce strike-slip faults of reversed polarity in the region opposite the pole. If the spreading ridge extended to the Lomonosov Ridge (LR), a strike-slip fault boundary is generated ± associated transtensive/transpressive features. Two plates with different spreading rates generate asymmetric basins, which is also a component of the Amerasia Basin. These results elucidate the consequences of sea-floor spreading in the Amerasia Basin and constrain opening scenarios.

Nilfouroushan, Faramarz

University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS. Geodetic infrastructure Department, Lantmäteriet, Gävle, Sweden.

Bagherbandi, Mohammad

University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.

Gido, Nureldin

Abstract [en]

Long-term monitoring of temporal gravity field and ground water level changes in Iran and its associated ground subsidence seen by geodetic methods are important for water source and hazard management.The high-rate (cm to dm/year) ground subsidence in Iran has been widely investigated by using different geodetic techniques such as precise leveling, GPS and interferometric synthetic aperture radar (InSAR). The previous individual SAR sensors (e.g. ERS, ENVISAT and ALOS) or multi-sensors approach have successfully shown localized subsidence in different parts of Iran. Now, thanks to freely available new SAR sensor Sentinel-1A data, we aim at investigate further the subsidence problem in this region.

In this ongoing research, firstly, we use a series of Sentinel-1A SAR Images, acquired between 2014 to 2017 to generate subsidence-rate maps in different parts of the country. Then, we correlate the InSAR results with the monthly observations of the Gravity Recovery and Climate Experiment (GRACE) satellite mission in this region. The monthly GRACE data computed at CNES from 2002 to 2017 are used to compute the time series for total water storage changes. The Global Land Data Assimilation System( GLDAS) hydrological model (i.e. soil moisture, snow water equivalent and surface water) is used to estimate Groundwater changes from total water storage changes obtiaend from GRACE data.

So far, we have generated a few interferograms, using Sentinel-1A data and SNAP software, which shows a few cm subsidence in western Tehran in last 2 years. We will try more Sentinel images for this area to better constrain the rate and extent of deformation and will continue InSAR processing for the rest of the country to localize the deformation zones and their rates. We will finally comapre the rates of subsidence obtained from InSAR and the rate of groundwater changes estimated from GRACE data.

Keywords

InSAR, subsidence, GRACE, deformation, Water

National Category

Geosciences, Multidisciplinary

Identifiers

urn:nbn:se:hig:diva-23352 (URN)

Conference

Fringe 2017, the 10th International Workshop on “Advances in the Science and Applications of SAR Interferometry and Sentinel-1 InSAR”, 5-9 June 2017, Helsinki, Finland

Abstract [en]

We use historical and recent major earthquakes and GPS geodetic data to compute seismic strain rate, geodetic slip deficit, static stress drop, the parameters of the magnitude–frequency distribution and geodetic strain rate in the Iranian Plateau to identify seismically mature fault segments and regions. Our analysis suggests that 11 fault segments are in the mature stage of the earthquake cycle, with the possibility of generating major earthquakes. These faults primarily are located in the north and the east of Iran. Four seismically mature regions in southern Iran with the potential for damaging strong earthquakes are also identified. We also delineate four additional fault segments in Iran that can generate major earthquakes without robust clues to their maturity.The most important fault segment in this study is the strike-slip system near the capital city of Tehran, with the potential to cause more than one million fatalities.

Abstract [en]

We run a series of analogue models to study the effect of stratigraphic heterogeneities of an evaporite formation on thin-skinned deformation of the Southeastern Pyrenean Basin (SPB; NE Spain). This basin is characterized by the existence of evaporites, deposited during the Early-Middle Eocene with lateral variations in thickness and lithological composition. These evaporites are distributed in three lithostratigraphic units, known as Serrat Evaporites, Vallfogona and Beuda Gypsum formations and acted as décollement levels, during compressional deformation in the Lutetian. In addition to analogue modeling, we have used field data, detailed geological mapping and key cross-sections supported by seismic and well data to build a new structural interpretation for the SPB. In this interpretation, it is recognized that the basal and upper parts of the Serrat Evaporites acted as the main décollement levels of the so-called Cadí thrust sheet and Serrat unit. A balanced restoration of the basin indicates that thrust faults nucleated at the stratigraphic transition of the Serrat Evaporites (zone with lateral variations of thickness and lithological composition), characterized by a wedge of anhydrite and shale. The analogue models were setup based on information extracted from cross-sections, built in two sectors with different lithology and stratigraphy of the evaporites, and the restored section of the SPB. In these models, deformation preferentially concentrated in areas where thickness change, defined by wedges of the ductile materials, was inbuilt. Based on the structural interpretation and model results, a kinematic evolution of the SPB is proposed. The kinematic model is characterized by the generation of out-of-sequence structures developed due to lateral stratigraphic variations of the Serrat Evaporites. The present work shows a good example of the role of stratigraphic heterogeneities of an evaporite formation which acts as décollement level on structural deformation in a fold-thrust belt. The results of this work have implications for hydrocarbon exploration and are relevant for studying structural geometry and mechanics in shortened evaporite basins.

Abstract [en]

The switch in direction of convergence between Central Iran and the Eurasian plate isbelieved to have a significant impact on the structural style in the Alborz Mountains, in northof Iran. To understand the deformation pattern and investigate the influence of the SouthCaspian Basin (SCB) kinematics since the middle Miocene on the structural styles and activetectonics of the Alborz Mountains, a series of scaled analogue models were prepared, wherepassively layered loose sand simulating the sedimentary units were subjected toorthogonal and subsequently oblique shortening by a rigid indenter. Model resultsshow that during the shortening an arcuate-shape foreland-vergent imbricate stack forms infront of the indenter. The orthogonal shortening is characterized by a prevailing right-lateraland left-lateral oblique-slip motion in the east and west of the model, respectively. This shiftin kinematics contradicts the proposed pre-neotectonic (orthogonal) model of the Alborz.However, during oblique shortening, model results show that deformation is mainlyaccommodated by left-lateral transpression within the sand wedge and by its internaldeformation. Oblique shortening is consistently accommodated by continued left-lateralmotion on the WNW-trending oblique thrusts, whereas the east-west trending thrusts and thepre-existing ENE-trending right-lateral oblique thrusts reactivate as left-lateral oblique faults.Precise monitoring of the model surface also illustrates partitioning of shortening into theforeland-vergent left-lateral thrusting in the south and hinterland-vergent back thrusting in thenorth. These model results are generally consistent with field observations and GPS data ofstructure and kinematics of the Alborz Mountains.

Abstract [en]

We performed a quantitative comparison of brittle thrust wedge experiments to evaluate the variabilityamong analogue models and to appraise the reproducibility and limits of model interpretation. Fifteenanalogue modeling laboratories participated in this benchmark initiative. Each laboratory received ashipment of the same type of quartz and corundum sand and all laboratories adhered to a stringentmodel building protocol and used the same type of foil to cover base and sidewalls of the sandbox. Sievestructure, sifting height,filling rate, and details on off-scraping of excess sand followed prescribedprocedures.Our analogue benchmark shows that even for simple plane-strain experiments with prescribedstringent model construction techniques, quantitative model results show variability, most notably forsurface slope, thrust spacing and number of forward and backthrusts. One of the sources of the variabilityin model results is related to slight variations in how sand is deposited in the sandbox. Small changes insifting height, sifting rate, and scraping will result in slightly heterogeneous material bulk densities,which will affect the mechanical properties of the sand, and will result in lateral and vertical differencesin peak and boundary friction angles, as well as cohesion values once the model is constructed. Initialvariations in basal friction are inferred to play the most important role in causing model variability.Our comparison shows that the human factor plays a decisive role, and even when one modeler re-peats the same experiment, quantitative model results still show variability. Our observations highlightthe limits of up-scaling quantitative analogue model results to nature or for making comparisons withnumerical models. The frictional behavior of sand is highly sensitive to small variations in material stateor experimental set-up, and hence, it will remain difficult to scale quantitative results such as number ofthrusts, thrust spacing, and pop-up width from model to nature.

Nilfouroushan, Faramarz

University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS. University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS. Lantmäteriet.

Abstract [en]

For about two decades, SWEPOS (the Swedish Permanent GNSS network) pillar stations have been used indifferent geodetic and geodynamic studies. To keep continuous measurements of these long lived pillar stationsand at the same time modernizing the SWEPOS network, it has been decided to install new truss mast stations,equipped with modern and individually calibrated antennas and radomes, capable of tracking all new GNSSsatellites. Installation of mast stations started in 2011. Today, each pillar station in the SWEPOS permanent GNSSnetwork has a close-by truss mast station, mostly in 10 meters distance with individual calibrated Leica chokering antenna and its attachment (LEIAR25.R3, LEIT). Due to their closeness to pillars, the modern mast stationsmay provide additional information for the analysis of ground movements in Sweden e.g. to distinguish betweentectonic and geodynamic processes (e.g. land uplift in Sweden).In this study, we have used two datasets from two different seasons for 21 pillars and 21 mast stations andformed different networks. The mast network has been processed using both IGS standard (type) and individuallycalibrated PCV (Phase Center Variation) models and therefore the effect of these two different PCV models onheight components has been investigated. In a combined network, we processed all 42 stations (21 pillars+21mast) to see how this multi-baseline network (861 baselines) combination differs from independent mast or pillarnetworks with much less baselines (210 baselines). For our analysis, we used the GAMIT-GLOBK softwareand compared different networks. Ambiguity resolutions, daily coordinate repeatability and differences betweenheight components in different solutions are presented. Moreover, the GAMIT and BERNESE solutions forcombined mast and pillar networks are compared.Our results suggest that the SWEPOS truss mast stations can reliably be used for crustal deformation studies.The comparison between pillar and mast stations shows similar time series for different horizontal and verticalcomponents and their Normalized rms (nrms) and weighted rms (wmrs) are almost equal.Comparison of standard and calibrated PCV models for mast stations show notable differences in height compo-nents and reach up to14 mm. These differences are antenna-dependent and are not systematic offsets. Therefore,whenever available, individual calibrated antenna models have to be used instead of standard (type) calibratedmodels.This study is part of the Swedish CLOSE III research project between Lantmäteriet, SP, and Chalmers Universityof Technology.

Brown, Dennis

Nilfouroushan, Faramarz

University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS. Geodetic infrastructure Department, Lantmäteriet, Gävle, Sweden.

Abstract [en]

Defining the structural style of fold-and-thrust belts is an important step for understanding the factors that control their long- and short-term dynamics, for comprehending seismic hazard associated with them, and for assessing their economic potential. While the thin-skinned model (no basement involvement) has long been the driving methodology for cross section construction and restoration of foreland fold-and-thrustbelts, a wealth of new geological and geophysical studies have shown that they are often thick-skinned, that is, basement-involved.